The present invention generally relates to regulators and, more particularly, to an intelligent regulator with input/output capabilities.
In the control of fluid in industrial processes, such as oil and gas pipeline systems, chemical processes, etc., it is often necessary to reduce and control the pressure of a fluid. Regulators are typically used for these tasks by providing adjustable flow restriction through the regulator. The purpose of the regulator in a given application may be to control flow rate or other process variables, but the restriction inherently induces a pressure reduction as a by-product of its flow control function.
By way of example, a specific application using regulators is the transmission and distribution of natural gas. A natural gas distribution system typically includes a piping network extending from a natural gas field to one or more consumers. In order to transfer large volumes of gas, the gas is compressed to an elevated pressure. As the gas nears the distribution grid and, ultimately, the consumers, pressure reducing stations reduce the pressure of the gas. The pressure reducing stations typically use regulators to reduce gas pressure.
Being capable of providing sufficient volumes of gas to consumers is important for natural gas distribution systems. System pressure, piping size, and the regulators typically determine the capacity of such systems, and system capacity is often evaluated using a simulation model. The accuracy of the system model is determined using flow data at various input points, pressure reducing points, and output points. The pressure reducing points significantly impact the capacity of the gas distribution system, and therefore simulating the pressure reducing points is important for the system model. These pressure reducing points, however, are within the distribution system and therefore are not considered custody transfer points (i.e., points at which the control of gas flow switches from the distribution system to the consumer). As a result, flow measurement is typically not provided at the pressure reducing points. Furthermore, since the pressure reducing points are not custody transfer points, the added cost of high accuracy is not required. Flow measurement problems similar to those described above with respect to natural gas distribution are also present in other regulator applications (i.e., industrial processes, chemical processes, etc.).
In addition, regulators are subject to failure due to wear during operation, thereby reducing the ability to control pressure along a pipeline. A damaged regulator may allow fluid to leak, thereby increasing fluid waste and possibly creating a hazardous situation. While damaged regulators may be repaired or replaced, it is often difficult to detect when a regulator has failed and determine which regulator is damaged. Detecting a failure and determining which regulator has failed is more difficult in a typical natural gas delivery system, where pipelines may run several miles. Accordingly, an apparatus that detects apparatus failure and identifies the location of the failure is greatly desired.
Additionally, distributed control is increasingly used for controlling industrial systems. In distributed control systems, control of component parts of a system, such as a gas pipeline system, for example, is performed within each of the respective components by including processing capability within the components. However, a central controller that communicates with components is still used to make control decisions for the system as a whole, program the system components, monitor system functions and mediate control between system components. Thus, although current distributed control systems provide some degree of autonomy to system components, the central controller still maintains a relatively high degree of control, especially when mediating between components of the system.